The present inventions are related to systems and methods for writing information to a magnetic storage medium, and more particularly to systems and methods for providing pre-compensation for use during a storage medium write.
Writing information to a magnetic storage medium includes generating a magnetic field in close proximity to the storage medium to be written. This may be done using a read/write head assembly as are commonly known in the art. One problem with such an approach to writing a magnetic storage medium is that the magnetic field generated during the write of a preceding bit pattern may interfere or otherwise affect a magnetic field generated during a write of a succeeding bit pattern. In particular, a magnetic field generated to write a current bit pattern may exhibit a non-linear transition shift (NLTS) caused by magnetic interactions between write-field and already written transitions. Presence of NLTS leads to data-dependent nonlinear distortions in the read back signal, causing degradation in data-recovery performance. Further, where NLTS becomes significant, the media exhibiting the NLTS may be disqualified, thus resulting in poor yield of the media.
Various systems employ a write pre-compensation scheme that considers preceding bit patterns in the process of generating a magnetic field to write a succeeding bit pattern. Such systems search over a multi-dimensional grid to determine the amount of any compensation to be added to a given write. The criterion used during the search process may be based on the error rate of the detector or another indicator. This searching process is, however, time consuming and becomes almost impractical for multi-level compensation scenarios where compensation for several potential patterns must be considered. Moreover, unlike the usual channel optimization tasks, such write compensation demands a separate write and read for each choice of the compensation. As a result, a relatively simple compensation scheme (e.g., a single level or a two level compensation scheme) is typically chosen to limit the complexity. Such simple compensation schemes are not, however, capable of providing the degree of compensation desired in some applications.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for write pre-compensation.